Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$97.62	9.385%	$106.7816	$106.78	$106.80	$106.80
Purchase #2	$82.27	8.523%	$89.2819	$89.28	$89.30	$89.30
Purchase #3	$58.29	6.197%	$61.9022	$61.90	$61.90	$61.90
Purchase #4	$51.75	8.836%	$56.3226	$56.32	$56.30	$56.30
Purchase #5	$198.31	10.498%	$219.1286	$219.13	$219.15	$219.10
Purchase #6	$195.38	6.699%	$208.4685	$208.47	$208.45	$208.50
Purchase #7	$244.35	6.376%	$259.9298	$259.93	$259.95	$259.90
7 purchase totals =	$927.97		$1,001.8152	$1,001.81	$1,001.85	$1,001.80